Method of refining waxes



' April :9, 1946.

WAXY OIL INLET Filed July 24, 1,941

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OUTLET Patented Apr. 9, 1946 METHOD OF REFINING WAXES Robert A. Macke, Roselle, and Herman J. Zoeller,

Union, N. J assignors to Standard Oil Development Company, a corporation of Delaware Application July 24, 1941, Serial No. 403,818

12 Claims.

The present invention is concerned with the refining of paraffin waxes which are segregated from petroleum or other mineral oil sources. The invention more particularly relates to an improved process comprising a particular arrangement and sequence of stages by which waxes having a high heat and light stability are secured. In accordance with a preferred modification of the present invention, petroleum crude scale waxes are acid treated in an initial stage, distilled over caustic in a secondary stage, and sweated in a tertiary stage under conditions to secure a high yield of refined waxes having an improved heat and light stability, 9

It is well known in the art to separate waxy constituents from petroleum oils by various processes and to refine the crude waxes separated by subjecting them to carefully regulated heat treat-- ment, usually in a sweater house. Separation of the waxy constituents from feed oils by conventional methods usually comprises chilling the waxy feed oil to temperaturesat which the wax crystallizes and passes out of solution, followed by filtering the chilled mixture. The waxes so obtained usually retain appreciable amounts of the oily constituents, the concentration of which may vary from about to about 50%;, or more, based upon the oily wax. These waxes, termed slack waxes, due to the amount of oil present; are semi-solid and unctuous in nature, particularly so when the amount of oil present is relatively high. The slack wax cake is removed from the filter press, melted in a suitable receptacle and conveyed in a molten state to sweating apparatus, the conventional form of which comprises a multiplicity of shallow metal pans stacked one above the other. Each pan is equipped with a false perforated bottom and a continuous coil ofpipe through which a heating or cooling, fluid may be circulated. The stack of pans is closed within the building, commonly known as a sweater house. The usual practice in charging the sweater pans is to fill each pan with water to the height of the false bottom which is withdrawn from thebottom of the pan after the wax charge has solidified. The molten: wax is then charged to the pan in such a way that it floats upon the water and that the interface between the wax and oil is slightly above the perforated plate. Under these conditions the pipe coil which is disposed immediately above the false bottom is submerged in the wax.

The molten wax is solidified by circulating cooling water, or an equivalent cooling medium through the. coil and by means of cool air which is-passed through the sweater house. After the crude wax is solidified, it is sweated and the oily constituents removed by gradually increasing the temperature of the oil-wax cake by circulating a heated fluid in the submerged coil and heated air within the sweater house. As the temperature of the crude wax cake rises, the oily constituents are first removed. After removal of an appreciable amount of the oily constituents, waxes of gradually increasing melting points are removed. These waxes contain gradually diminishing percentages of oil as the sweater house temperature and the melting points of the fused waxes increase. Finally, the sweating operation progresses to the point where only the porous structure of the highest melting point wax remains in the solid stage on the perforated false bottom since the other wax fractions have melted out and have been drained off by grades to storage receptacles. The remaining solid, relatively high melting point wax is substantially oil-free and is known in the art as crude scale wax. Crude scale wax contains approximately 2% of oil based upon the wax and is hard and firm, and generally possesses some discoloration. This crude scale wax is subjected to further sweating in order to remove the remainder of the oil, and to produce a refined high grade wax.

However, the refined waxes secured by a subsequent sweating of the crude scale Wax are not entirely satisfactory with respect to their stability when subjected to heat and light. The instability of these waxes is a particular disadvantage since it renders them unfit for many uses, such as the coating of paper for use in conjunction with the handling of food materials. The instability of petroleum Waxes with respect to heat and light is aggravated when the waxes are secured from particular crudes such as a Panhandle crude, a Salt Flat crude, or a Reagan type crude.

In order to overcome these inherent disadvantages and to improve the quality of the final wax produced various proposals have been made. For example, in the conventional procedure slack wax is acid treated, neutralized, and water washed, followed by sweating to crude scale, which in turn is sweated to refined wax. An alternate processing scheme involves acid treating the crude scale, caustic neutralizing, and water washing, followed by sweating to refined wax. However, these operations do not produce a final wax product which has a satisfactory heat and light stability when the wax is derived from said specific crude sources.

We have, however, now discovered that providing a particular sequence and arrangement of any conventional procedure.-

. of line I.

tic providing a critical amount of caustic be employed, a preferred modification of our process comprises acid treating crude scale wax, remove, ing the acid, rerunning the acid treated product over excess caustic, followed by sweating the overhead product under conventional conditions to produce a refined wax product of especially high quality. i

The process of our invention may be readily understood by reference to the attached drawings illustrating embodiments of the same. Figure 1 illustrate a preferred modification of our process wherein crude scale wax i acid treated,

the acid treated product distilled over excess.

caustic to produce an overhead product which is sweated for the production of our highly refined stable wax. Figure 2 illustrates an adaptation of our invention wherein the slack wax is distilled over a critical amount of excess caustic, the overhead or side stream sweated to produce slack wax which is acid treated, neutralized, water washed, and sweated to produce the final product. Referring specifically to th drawings it is assumed for the purpose of description that the waxy constituents are segregated from a petroleum oil such as a Panhandle petroleum oil by a solvent dewaxing operation. The waxy petroleum oil is introduced into dewaxing zone I by means of line 2 while the dewaxed oil is withdrawn by means of line l. Dewaxing zone I may comprise any suitable number and. arrangement of units and the waxy constituents may be segregated by Slack wax having about 25 oil is withdrawn from dewaxing zone I by means of line 4 and passed to sweating zone 5 wherein the same is sweated to remove oil constituents from the wax. The segregated oil con- 'stitue'nts are separated by means of line 6 while so called crude scale wax'is removed by means In accordance with our process the crude scale wax ispassed to acid treating zone 8 wherein the same is acid treated with a suitable mineral acid which is introduced by mean of line 9. The spent acid and sludge are withdrawn by meansof line H). For the purpose of descrip-' tion it is assumed that the mineral acid comprises sulfuric acid having a concentration of about 90%. The acid treated wax is removed from zone 8 and combined with caustic which is 1 introduced by means of line 13. The wax and the the same is sweated to remove the final traces of 011... The oily constituents are removed by means of line I! while the refined wax of exceptionally high quality is removed by means of line It.

,Referring specifically to Figure 2, it is assumed 7 that the waxy constituents are segregated from Our wax is, therefore, very desirable for V a waxypetroleum oil employing a solvent dewaxing operation. The waxy oil is introduced into dewaxingzone 20 by means of line 2| while the dewaxed oil is withdrawn by means of line 22. The slack wax constituents comprising about 25% of oil are withdrawn from dewaxing zone 20 by' The slack wax is combined spent'caustic i removed with the bottoms from the distillationfzone by means of line 25, an overhead fraction by means of line 21', while the desired'waxy constituents are removed as a side stream by means of line 28. The desired waxy constituents removed by means of line'28 are passed to sweating zone 29 wherein the same are sweated to separate oily constituents which are removed by means of line 30 and to produce a crude scale wax which is removed by means of line 3|. The crude scale wax is acid treated in acid treating zone 32 by'means of sulfuric acid which is introduced by means of line 33 and with drawn by means of line 34. The acid treated oil is neutralized with substantially an equivalent amount of caustic in neutralization zone 35 with an alkaline reagent which is introduced by means of line 36 and withdrawn by means of line 31. The waxy constituents are then water washed in washing zone 38 with water which is introduced by means of. line 39 and withdrawn by means of line 40. The crude scale wax is sweated in sweating zone 4| to remove the remaining oil constitu ents which are separated by means of line 42 and to produce a highly refined wax of increased stability which is removed by means of line 43.

The process of the present invention may be widely varied. It is to be understood that the respective zones may comprise any suitable number and arrangement of units. -The-invention essentially comprises distilling the wax over. caustic, preferably an alkali metal hydroxide solution, or suspension. Alkali metal carbonates as, forexample, sodium carbonate may also be employed. Although the slack 'wax may be distilled over caustic, it is'preferred to sweat the slack wax to produce crude scale wax, which product is distilled over caustic. T

Although the operation may be adapted for the treatment of waxes segregated from any mineral oil, it is particularly suitable for the treatment of waxes separated from petroleum oils, especially of the Panhandle type, which waxes are quite imstable with respect to heat and light.

The slack waxes segregated from petroleum oils by conventional operations usually contain fromabout 5%to 50% of oil. These waxes when sweated yield from about 25% to crude scale wax, based upon the slack wax. The crude scale waxes when sweated result in a yield of about pounds of acid per hundred gallonsof wax. In

general, it. is preferred to contact the wax and the acid at a temperature in the range from about 7 F. to about 200 F. The alkali solution e'm-.

ployed in :thedistillation:stage and in the neutralization stage may compriseany suitablealkali. In the distillation'stageyan excess amount :of the alkali .is employed whereas in the neutralization stage an amount is used which is necessary to neutralize the acidic constituents. Although potassium hydroxide .or sodium carbonate solutions may be employed, we prefer to use sodium .hydroxide solutions-such as those having a concentration in the range from about 34" to about 38 Baum. When utilizing'excess sodium hydroxide it is preferred to use from 0.05 to'0;5% excess. For example, when directly distilling the slack wax over causticthe amountof excesscaustic employed should be in-the rangefrom about 0.2 to 0.3%. Also about 0.05 to 0.1% excess caustic should be employed with the acid'treat'ed crude scale wax. The distillation operations over the caustic are conducted under either atmospheric or'vacuum conditionsand at a coil outlet temperature in the range from-about 600 F. tea-bout In order toillustratethe invention further, the following examples are given which should not be construed as limiting thesame in any manner whatsoever:

EXAMPLE 1 A crude scale 'wax was acid treated employing 40 pounds of 98% sulfuric acid per 100 gallons,

of wax. The acid treated wax had the following inspections:

Melting point, F 137 Per cent oil (A. S. T. M.) 2.3

The acid treated crude scale sweated to a refined wax yield of 27.2% on scale and bauxite filtered to 25 tons per ton'yield. had theiollowing inspections:

Inspection-of bauxite filtered refined 'waa:

Heat stability: The wax is maintained at 302 F.'for 16 hours in themrcsence of copper'strip and the color of the wax is then determined.

2 Light stability A cake of wax inch thick is exposed for 7 days to a Westinghouse Sterilamp at room temperature and the color then determined;

In each of these tests a final color of to 10 Saybolt 7 is considered the lower limitffor a satisfactory wax.

In other operations" the acid treated wax was Ccustz'cireatmentbj iwaa: Rerunnin'g acid treated crude scale 40#' 08% acid/100 ar I. g 1 Per cent excess NaQH 1 0.1 "0.25

in accordance with the present process are readily apparent by the decided improvement secured with respect to color which may be readily appreciated when Saybolt colorand Tag Robinson color are correlated 'on' an absolute color scale as follows:

Saybolt Tag Robin'- color 1 son.

, Absolute color'scale EXAMPLE 2 In other operations, slack Wax was distilled over caustic under under conditions *to remove overhead 25% of'the 'feed and to remove as a bottoms about 5% of the feed. of the slack wax was removed asa side/stream. The sweated sidestream product was acid treated, neutralized, water washed,.and.sweated to produce a refined wax which was bauxite filtered. .The results of these operations were as follows:

Caustic treatment of was:

Rerunning of slack wax M. P. "F. 109% oil 42.1:

Percent excess NaOH Coil outlet, "F Maximum still temp., "F

Percent side stream over 5% bottoms Inspections of side stream:

Melting point, F Percent oil (A. S. T. M)

Sweating to crude scale:

Percent yield Melting point, F Percent oil (A. S. 'I.

Sweating acid treated crude scale (40;? 98% acid/100 gal.): Percent yield refined wax.

Inspections of bauxite filtered refined war (25 T/T yield): Melting point, "F Percent oil (solvent dilution method) Color, Saybolt Heat stability, color +30 +30 4-30. 10 Tag Robinson 12 Tag Rohinsom. +3 Saybolt... 8 Tag Robinson.

Light stability, color 21 Tag Robinson... 21 Tag Robinson... +12 Saybolt... 19 Tag Robinson.

distilled over excess caustic, sweated to refined wax, followed by bauxite filtration, under the conditions given above. The results of these operations were as follows:

From the foregoing it is apparent that material advantages with respect to stability are secured by refining the wax in accordance with the present process.

' prises a sulfuric acid In the appended: claims, the expression paraffin wax" is intended to mean either crude or refined petroleum wax of the crystalline type as. obtained from the paraflindistillate cut, especially from paraflinic crude oils, andincludes slack wax, crude scale wax or refined paraffin wax.

What we claim as new and wish to protect by Letters Patent is: 7 3 v I 1. Process for the production ofparaifin waxes of. improved heat and light stability which-comprises segregating from wax-containing petroleum oils a wax fraction .contai'ningnot' more than about 50% of oil, distilling thesameover excess sodium hydroxide solution, and recovering an overhead of improved heat and light stability. I

' '2. Process for the production of highly refined 4. Process as defined by claim 2 in which said wax is "distilled over about 0.1% excess sodium hydroxide. 7 V

5. Process for the production of highly refined waxes which comprises distilling slack wax over; an' appreciable excess of an alkali, segregating a sidestream, sweating said side stream to produce crude scale'wax, acid treating the crude scale wax, neutralizing the same, then sweating the neutralized product to produce said refined wax. r v

6. Process as defined by claim in which said 'excess alkali comprises about 0.25% excess sodium hydroxide and in which said acid comfrom about 80% to about 104%. r I r 7. Process for refining a crude wax of the class consistingof slack wax, and crude scale Wax,- derived from a crude petroleum of the typeof Pan handle, Salt Flat and Reagan crudes, which comprises subjecting said crude wax to distillation with a slight excessof caustic soda of about 34-38 Baum at a temperature of "about 600800 F. to a bottoms fraction of about 5-7%. u8.j.Process for the production of a highly refined .paraflin wax from a crude scale wax derived from a crude petroleum of the type of Panhandle, Salt Flat and Reagan crudes, which comprises acid treating said crude scale wax with about 3-50 lbs. of about 83-104'% sulfuric acid per 100 galions of wax at a temperature of about ISO-200 F., removing the spent acid and sludge, distilling the acid treated wax over an excess of about .05-.10% of caustic soda of a concentration of about 3438 Baum to abottoms of about 5-7%, and sweating and filtering the wax distillate,whereby a refined paraflin wax is obtained having satisfactory heat andv light stability as determined in tests substantially as described. V

. 9. Processfor the production of a highly refined parafiin wax from a slack wax derived from centration, at a temperature of about'600-800" F.

to remove a bottoms fraction of about 5'7%, sweating the wax distillate to'a' crude scale-wax, acid treating the latter, with about 3-50 lbs, of sulfuric acid of about ,83104% concentration per 100 gallons of wax at about 150- 200 F., removin the spent acid and sludge, and neutralizing, washing, sweating and filtering the acid treated wax to produce a highly'refined paraiiin -wax having satisfactory heat and light stability as determined by the tests substantially as described. ;10. Process for the production of a refined Daraflin wax which comprises segregating slack wax from petroleum oils containingthe same, sweat-5 ing said slack wax to produce a crude 'scale'wax, distilling said crude scale wax overexcess caustic to remove a bottom fraction of about 5 to 7% and recovering overhead a refined wax of improved heat and light stability,

'11. Process which comprises acid treating a 7 Crude scale wax, sweating same to a refined wax,

bauxite filtering said refined wax, distilling said filtered refined wax over excess caustic and. recovering overhead a refined wax of improved heat and light stability.

12. Process according to claim 11 in which the final distillation overhead is subjectedto further sweatingand filtering steps.

ROBERT A. MACKE, J. ZOELLER. 

